Nitrogen-doped MoS2 as a catalytic sulfur host for lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) are the leading candidates for the next-generation lithium-ion batteries because of their large energy densities and low price. However, LSBs have a critical problem in that specific capacity continuously decreases due to the shuttle effect, so it has not been commercialized. Herein, we propose an N-doped MoS2 composite (nMC) with the dual functions of a chemisorption host and a conversion catalyst to inhibit the shuttle effect and thus improve the scalability of LSBs. The nMC increases the chemisorption energy of lithium polysulfide and promotes electron transfer, resulting in improved cycle stability and electrochemical performance. In addition, it controls the redox kinetics of lithium polysulfides by acting as a catalyst of the cathode. The nMC cathode accelerates the reaction rates by reducing the activation energy barrier of the Li2Sn to Li2S conversion and inhibits the shuttle effect by rapidly reducing highly soluble Li2Sn. Consequently, we developed the N-doped MoS2 composite, a catalytic host material for LSBs, that provides high initial capacity, outstanding cycle stability, and fast charging ability as cathode materials of LSBs. Especially, LSBs based on S@nMC cathode demonstrate high cycle stability with a low-capacity decay rate of 0.025% per cycle after 1000 cycles.